One form of chemical detection device employs spectroscopic-based techniques. For example, such a device samples air by passing it through a filter having a surface coating adapted to adhere to the chemical vapors being detected. The filter traps molecules of the chemical vapor being detected and is then burned (i.e., vaporized) to produce a light spectrum indicative of the presence or absence of the chemical vapor being detected. A spectrometer is then employed to split the various wavelength components of the light spectrum due to the vaporization of the chemical vapor. The spectrometer produces a pattern of lines characteristic of the presence or absence of the chemical being detected. The mass spectroscopic-based systems available today, however, tend to be too large and require too much power to be field portable.
Another type of chemical detection device employs quartz crystals as mechanical oscillators. Such devices generally measure the change in frequency of an oscillating quartz crystal as it is affected by the mass of molecules which are being detected. The change in mass, however, of quartz crystal oscillators as they absorb chemical vapors, is so small that the change in their frequency of oscillation is also extremely small. This limits the sensitivity of quartz crystal-based detection devices and the number of different applications in which they can be reliably employed.
It would be useful to be able to provide a sensing technology that is highly sensitive, power efficient, and compact in size (e.g., nanometer scale).